864 SKELETON 
mentioned is a deep cavity crossed by a transverse bridge, acting as 
a pulley for the tendon of the muse. extensor digitorum communis 
(page 612) which passes beneath it. In the majority of Birds 
this bridge is ossified, as in Dinornithes (page 579), Phororhacos, 
rastornis (page 281) and the other Carinate not named below, but 
it remains tendinous or cartilaginous, and is thus often described 
as non-existent, ina good many, as Struthio, Rhea, Dromeus, Casuarius, 
Aipyornis, Brontornis, Opisthoconus, Striges, Todus, Buceros, Caprimulge 
and Trochili ; while it varies, being either soft or osseous, in Apterya, 
Podicipes and Psittact. 'The Fibula articulates by its head with the 
outer condyle of the Femur, leaning also on the lateral knob on the 
head of the Tibia, and lower down is connected with the peroneal 
ridge by a rough surface. The distal end of the Fibula is always 
much reduced and fuses more or less completely with the outer 
side of the tibio-tarsus, generally ending in a sharp point.! 
The Metatarsus, or “ Tarsus” as it is commonly but incorrectly called 
by ornithologists, is a compound structure made up of the second, 
LO; 
MCs 
Pavo. Tibia and Tarso-metatarsus, Proxiiialiacendiaeotmelest 
front view. Tarso-metatarsus, back 
F, Fibula; [.a.c. and O.a.c. inner and view.—F.p. groove and 
outer anterior crest; m.i. mae. canal for m. flexor pro- 
inner and outer malleolus; Sp. fundus; P.p. groove for 
exostosis, carrying spur; T.a. in- deep peroneal; T'.4. 
sertion of Tibialis anticus. ridge for tendo Achillis. 
1 Dr. Shufeldt (Jbis, 1894, p. 361) takes exception to the statement previously 
made in this volume (page 249) describing and partly figuring some cases, that 
appear to me exceptional if not abnormal, in which the Fibula is ‘‘ complete 
and reaches the tarsal epiphysis of the tibio-tarsus.”’ But my statement appears 
to have been misunderstood, and I may repeat that the ankle-joint ‘‘is never 
normally reached” by the Fibula, nor, for the matter of that, by the Tibia 
either. A complete account of these features was published in 1891 (7Thier- 
reich, Vogel, pp. 980, 981), wherein also exceptional occurrences of a complete 
Fibula in Birds are mentioned. 
